Insulating housing



I May 7, 1935.. F CQMSTOK' 2,000,882

INSULATING HOUSING Original Filed Sept. 7, 1928 2 Sheets-Sheet l 26/ iifz fla 2.

Daniel F Comsloc y 9 r o. F..coMsTocK' 2,000,882

INSULATING HOUSING Original Filed Sept. 7, 1928 2 Sheets-Sheet 2Patented May 7, 1935 INSULATING HOUSING Daniel F. Comstock, Boston,Mass., assignor, by mesne assignments, to Stator Refrigeration, Inc., acorporation of Delaware Original application September 7, 1928, SerialNo. 304,589. Divided and this application March 20, 1930, Serial No.437,377

4 Claims.

This invention relates to insulation as applied to or incorporated inrefrigerators, refrigerator cars, refrigerant ducts, hot or cold fluidpipes or tanks, heaters, boilers, houses, or other installations, andmore particularly as associated with the former. This application is adivision of my copending application No. 304,589, filed September 7,1928, and all of the specification and disclosure of that applicationare included by reference in the present application.

While it has heretofore been proposed to utilize vacuum chambers forinsulating refrigerators or the like, the diificulty of permanentlymaintaining a comparatively high vacuum in housings of this characterhas made the commercial provislon of such insulating means impractical.The present invention provides vacuum insulation for purposes of thischaracter, preferably utilizing a fairly high vacuum in conjunction withpowdered or closely spaced filling material or other material Iiavingminute interconnected voids in the vacuum chamber.

The elements of this filler material may be so disposed in indifferentparticle-to-particle contact that they afford a very poor path fordirect heat conduction between opposite sides of the vacuum chamber,while preventing direct heat radiation between the same and providingonly a low rate of reradiation. The voids in the filler materialpreferably have dimensions substantially less than the mean free path ofthe gas molecules. The filler is also preferably non-hygroscopic and nothighly gas absorptive. When material of this character is located withina vacuum chamber, a considerably lower vacuum provides as good a heatinsulating efficiency as does a high vacuum in chambers that are freefrom the separated or foraminous filler.

One of the deficiencies of vacuum insulating walls or casings of thecharacter heretofore proposed has been the freedom with which heat couldpass from one wall of the vacuum chamber to the other by paths otherthan through the vacuum space'itself; for example, the wall connectinghot and cold sides of the chamber have usually provided such a lowresistance to the flow of heat that the effect of the vacuum insulationwas substantially nullified. Thus, for example, invacuum insulatingwalls of the character heretofore built or proposed it has been commonto provide continuous metal connections between the opposite hot andcold Walls of the chamber, the metal of these connections being ofsubstantially the same thickness as the opposite hot and cold walls orface sheets of the vacuum chambers and conse quently providing paths ofhigh heat conductivity between the hot and cold sides of the insulatingwall. The present invention preferably obviates these deficiencies byproviding bridges or connections of low heat conductivity between theface sheets or metal walls at opposite sides of the vacuum chamber.Thus, for example, I may provide non-metallic supporting elementsbetween the margins of the inner and outer walls, which are adapted tosupport the same against the external atmospheric pressure and I mayassociate comparatively thin metal bridges with these nonmetallicelements, the bridges preferably being formed of metal having high heatresistivity Thus the thin metal is united with the opposite face sheetsin order to provide a substantially gastight seal, while the thinness ofthe metal as well as its natural heat resistivity causes it to-afford acomparatively poor heat conductive path. The non-metallic supportingmaterial which permits the use of the thin metal bridges preferably maybe a comparatively poor heat conductor. It is thus evident that ahousing having walls formed in accordance with this invention ordinarilywill be characterized by parallel metal sheets which normally may be atquite different temperatures, having their edges connected by bridges oflow conductivity whereby there is only a slight leakage from the hightemperature to the low temperature sheet.

As a further adaptation of my invention, I preferably provide similarbridges or connective means not only betweenthe edges or margins of thesheets, but at openings which are provided for the necessary pipes orthe like that may pass through the wall to provide connections forrefrigerant flow or the like and at other locations.

When an insulating wall is filled with material having minuteinterconnected voids, it may prove somewhat difficult to cause acontinuous gas flow from all portions of the chamber thus filled to asingle gas outlet. Therefore, in its preferred embodiment my inventionprovides the vacuum chamber with suitable air or gas passages arrangedin conjunction with the filling material to permit the circulation ormovement of gas from widely spaced regions within the insulating wall tothe single gas outlet. Thus, for example, I may preferably provide airpassageways which are substantially coextensive with a face of the wallitself. These passageways communicate with a duct that may be connectedto any suitable evacuating means such as that, for example, dis-. closed.in my copending application referred to above, so .that the pumpingmeans may be continuously operable to maintain a fairly high vacuum inthe insulating wall to compensate for leakage into the chamber, or, ifdesired, this duct may be connected to means arranged to evacuate thechamber.

In the accompanying drawings:

Fig. 1 is a front elevation of a refrigerator in which my invention maybe incorporated;

Fig. 2 is a broken horizontal -section indicated by line 2-2 of Fig. 1;

Fig. 3 is an elevational detail of the screen and fabric arrangementprovided to permit the ready evacuation of the vacuum wall or casing;

Fig. 4 is an elevational detail of the vacuum casing;

Fig. 5 is a section on line 5-5 of Fig. 4;

Fig. 6 is a perspective detail of a corner portion of an optional formof frame for a casing of this character;

Fig. 7 is a vertical section through a portion of a door showing anoptional construction of the same; and

Fig. 8 is a section through a door having a heat non-conductive bridgeof the type shown in Fig. 6.

Referring first to Figs. 1 and 2 of the accompanying drawings, it may beseen that the refrigerator housing is provided with inner and outerwalls which afford a suitable space therebetween which may be exhaustedof air, gases, and vapors, thus providing a comparatively high vacuum;This space is preferably filled with closely spaced, finely divided orforaminous material which is a poor transmitter of heat, such ascomminuted diatomaceous earth, which may be pressed into bricks, closelyspaced sheets of paper, attenuated fibrous material or the like, cork orsimilar porous material, which not only prevents direct radiation fromone wall of the vacuum chamber to the other, but which minimizes theeffect of reradiation and which affords small voids which at a propervacuum are substantially smaller than the mean free path of the gasmolecules. Radiation is also minimized, because each particle canordinarily radiate only to a juxtaposed particle or particles. Suitablegas-collecting passageways may be arranged within the vacuum chamber ina manner which will be described below, these passageways beingconnected to the air exhaust pipe 1. The latter may be connected to anysuitable evacuating means, such as the first stage of the multi-stagepumping means illustrated in my above identified application, or to anydesired type of vacuum pump.

As shown more particularly in Fig. 2 the refrigerator housing I isprovided with the inner and outer shells 2 and 3 which may convenientlybe formed of sheet metal and which are nested in spaced relation to eachother to provide a vacuum chamber therebetween. The box is preferablyprovided with a suitable swinging door or closure I10 which alsocomprises a vacuum chamber that is connected by a suitable duct with thechamber in the housing proper. The inner sheet metal casing 2 may carrya plurality of spacing elements or struts l1l of hard non-conductingmaterial, such as bakelite, asbestos wood, hard rubber, or othermaterial which preferably is rendered impervious to moisture. SpacersI'll may be secured to the inner shell 2 by means of metal clips I12which are soldered, welded, or otherwise joined to the shell.

Located along the inner face of the outer shell 3 are suitable means toprovide fluid passages which may connect with the pipe 1. These passagespreferably are arranged to permit the exhaustion of gas and vapor fromwidely spaced and distributed portions of the vacuum chamber. One modeof attaining this result consists of the provision of meshed wirescreening I14 held against the face of the metal shell by clips I15.This screening preferably may be substantially coextensive with theouter face of the shell wall, and similar screening, similarlydesignated, may be arranged within the door I10. A suitable fabric 201,such for example as felt, may be arranged against the wire screen l14,this fabric preferably being sufliciently impervious to prevent thefinely divided filling material from penetrating into the air spacesbetween the wires of the meshed screen, while readily permitting theflow of gas.

As previously stated, the finely divided or foraminous filler materialpreferably is packed between the inner and outer walls of the vacuumchamber. Such material, for example, may be diatomaceous earth, closelyspaced sheets of paper, closely packed fibrous material, or similarsubstances, which are adapted to prevent the movement of heat byradiation between opposite walls of the vacuum chamber and which mayprovide interconnected voids having dimensions substantially less thanthe mean free path of the gas molecules.

The outer ends of spacers or struts l1| engage the sheet 201, aiding inholding the same in place. The filling material packed between thefabric and the inner shell and about each of the spacers also aids insupporting the walls against the external atmospheric pressure, and withproperly reinforced walls of the internal reinforcements or spacers l1|may be omitted and dependence placed upon the filling material alone forthis purpose, if desired. Fig. '7 illustrates a door having asubstantially solid filler which may conveniently be diatomaceous earthin the form of bricks or blocks 40 which forms suitable reinforcementsfor the opposite sheet metal walls of the chamber, so that the internalreinforcements or struts "I are ordinarily not required when this 'formof the invention is employed, the screen I14 and fabric 201, however,may be employed as in conjunction with'the finely divided fillermaterial, or the brick may be scored or roughed to provide air passagesbetween the brick and the metal sheets and between the bricksthemselves.

Special means are provided between the edges of the inner and outershell to prevent heat conduction therebetween, thus materially raisingthe heat insulating efficiency of the housing. For this purpose, Ipreferably arrange the edges of the inner and outer shells in spacedparallel relation and provide especially constructed non-conductivebridges therebetween. In the specific arrangement illustrated herewith,for example, the edge of the inner casing 2 may be turned outwardly toprovide a. perimetric flange I83 while the edge of the outer casing isinturned to provide a flange I84. The form of non-conducting bridgewhich is illlustrated therewith may comprise strips I05 of heatinsulating material such, for example, as bakelite, asbestos wood, hardrubber, or various other synthetic compositions, or natural woodimpregnated with suitable moisture-resistant material, such for exampleas high boiling point paraffin. The inner and outer edges '01 thesebridge elements preferably may be enlarged and may receive sheet metalchannels I86, the outer edges of the legs of which are firmly flangedabout the enlarged portions of the nonmetallic elements as designated bythe numeral I8I. A suitable filler strip 22I maybe arranged between theinturned metal portions I81 to provide a surface substantially alignedwith the aligned surfaces of metal strips I88. A thin metal plate 220may then be secured by soldering or the like to these aligned surfacesof the strips I88, this metal plate being supported by the filler 22Iand serving to provide a substantially gas-tight seal between the twostrips I88. The sealing strip 220-preferably is formed of metal havinghigh heat resistivity such as, for example, constantan, nichrome, invar,or the like, and preferably is of thin gage in order to provide low heatconductivity. The non-metallic element I85 supports the opposite edgeportions of the metal walls against external pressure so that the metalsealing strip 220 does not need to have great structural strength andaccordingly may be made quite thin.

One of the strips I88 upon each of the bridges I85 is secured bysoldering or welding to the flange I83, while the opposite metal portionI88 is secured to a rectangular frame I89 of sheet metal. Preferablyflange-I84 and frame I89 lie in the same plane and are spaced fromeachother. A suitable cover frame I90, which also preferably isrectangular, may then be soldered or welded upon the outer faces offrame I89 and flange I84, thereby closing the space between casings 2and 3. Thereafter any conventional outer sheathing or covering means maybe provided as, for example, the outer sheets of veneer or decorativemetal IBI and the comer trim I92 and the edge strips I93.

The door preferably is formed of inner and outer metal sheets 280 and28I, the screen Ill being arranged adjoining the inner face of' thelatter. Suitable spacers III may be arranged between the inner and outersheets after the manner described above with reference to the mainvacuum chamber. The bridge elements I85, which are arranged within thedoor, may correspond to the similar strips similarly designated anddescribed above, and similarly may be associated with non-metallicfillers HI and thin metal sealing plates 228. The inner metal portion ofthe bridge strip within the door may be welded to a marginal face of theinner sheet 208, while the outer metal element may be secured to therectangular frame I91, this frame being secured by soldering, welding orthe like to the edge of sheet 2M. The door may be provided with suitablecovering means and flanges in any desired manner, as shown.

The bridge members may conveniently be assembled to compose rectangularframes before they are disposed between the inner and outer sheets orbetween the face sheets of the door.

For this purpose the strips I and the channels I88 are provided withmitered joints, Fig. 4, and slots 208 are cut in the mitered ends of thenonmetallic elements I85, these slots preferably extending the fulldepth-of these elements, as indicated in Fig. 5. A comparatively stiff,impervious sheet material, which may be impregnated by a high meltingpoint paraflin or the like, may be folded to provide an angle element881 which is engaged in the slots at the ends of the strips I88;pressphan or fish-pam'r or similar material is suitable for thispurpose, since it is comparative- -ly stiff and sturdy and yet hassufficient yieldability to permit its introduction into the slots 208.When the bridge strips are thus assembled in this manner, the adjoiningportions of' the metallic channels I88 may be secured to each other bysoldering or welding, as designated by numeral 205, Fig. 4. The sealingstrips 220 which meet at the corners may then also be welded orotherwise secured to each other to provide a substantially continuousmetallic seal. It is evident that the rectangular bridge frame utilizedin the door is similar to that provided for the casing, but that thesealing strips 228 are located about the bridge frame in the former caserather than inside the same as shown in Fig. 6.

Bridges similar in general construction to those flow between oppositesides of a wall of the hous ing- Thus, as shown in Fig. 2, a cooler 8|may be connected by a pipe 82 extending through the back of therefrigerator housing to any suitable exterior refrigerating means. Witha pipe of this character which necessarily passes through the vacuumwall, suitable circular openings may be cut in the inner and outersheets with a diameter somewhat larger than that of the pipe. An annularor spool-like bridge of any desired composition, such as hard rubber,wood, bakelite, asbestos wood, or the like is arranged between the innerand outer sheets at this point, suitable metal channels having theirlegs clinched about enlarged portions of the annular member in the samegeneral manner, as described in reference to the bridges at the edges ofthe box with the exception that these members are curved rather thanstraight. Thus the outer metal member I85 may be soldered or welded tothe face of sheet 3 adjoining the pipe opening therein, while thecorresponding opening in theinner sheet may portions of the channels I85and I88 inside of the annular bridge member, and a metallic seal-. ingstrip 220* may be soldered or otherwise secured to the aligned surfacesof the channels I88, this strip being supported by the flller 22h.

A suitable ring of heat insulating material 28I is arranged within theannular member and is adapted to hold the pipe 82 in spaced relationthereto and spaced from the inner and outer walls of the vacuum chamber.If desired. this portion of the pipe may be made of material having lowheat conductivity, such as constantan, nickel-chromium, or invar, and/or may have thin walls.

In order to permit the flow of gas from the air passages provided, bythe meshed screen in the door to the corresponding passages within thechamber, I provide a suitable flexible duct 2II which is connected tothe interior of the door and the interior of the chamber. This duct-maybe formed of a single metal tube with an undulatory wall of the typecommonly utilized for metal bellows or the like, the ends of this tubebeing welded, brazed, soldered, or otherwise secured to the outer walls8 and NI of the housing and door respectively and the ends of this tubebeing arranged in somewhat spaced relation from the bridge construction.As in the case of the construction shown in Fig. '5 these connectingbridges may be utilized both between the inner and outer shells of thecasing and the inner and outer walls of the closure, Figs. 6 and 8illustrating the latter specifically.

In order to minimize heat conduction between the inner sheets 300 andthe outer sheets 30!, it is desirable to use material having low heatconductivity, to make the path to be traversed by the heat comparativelylong, and to minimize the cross-sectional area of the conductive path.Accordingly when metal is utilized for this purpose I preferably providea bridge sheet 302 which may be of a gage considerably thinner than thatof the outer and inner sheets 300 and 30L This sheet preferably hasportions welded or otherwise secured to the edges of the sheets 300 and30! and is preferably formed of metal having low heat conductivity, suchfor example as constantan or nichrome. Furthermore this metallic bridgemay be arranged to follow an indirect course between the inner and outersheets 300 and (MI. For this purpose I may arrange a plurality of fillerelements 304 in channels formed in the sheet, the adjoining channelsfacing in opposite directions and being reinforced by the fillerelements 304 that fit tightly wi hin the same. These elements may be ofany suitable material having low heat conductivity, and may convenientlybe formed of material adapted to withstand considerable heat so thatthey may be heated when the chamber is initially evacuated. Asbestoswood is therefore suitable for this purpose.

Suitable non-conductive finishing material 308 may be arranged about thebridge strip 302, as shown in Fig. 8.

Fig. 6 illustrates a typical corner construction in a door having ametallic bridge of the type shown in Fig. 8, it being understood thatthe channels may be built up and welded together at the corners in orderto make the same substantially continuous about the perimeter of thebridge frame. It is evident that the construction shown in Figs. 6 and 8permits the provision of a metallic bridge between an inner and outerwall of the vacuum casing which may remain at different temperatures.The heat resistivity of the bridge metal as well as the length of thesame, and the thinness thereof thus may cooperate in permitting only aslight heat flow between the inner and outer sheets.

From the foregoing it will be evident that this invention provides aninsulating wall or housing which may contain one or more vacuum chambersthat preferably are filled with closely spaced, or foraminous non-heattransmitting material and which are exhausted to a fairly high vacuum;that this invention is suited to the provision of a commerciallyfeasible type of wall that need not be absolutely free from atmosphericleakage, but which may receive a small amount of gas either from theatmosphere or from the metal of the vacuum chamber walls, suitablepumping means such as disclosed in my above identified copendingapplication then being connected to the duct 1 continuously to maintainthe vacuum within the chamber. It is further evident that my inventionpermits the ready removal of gas from all portions of the evacuatedchamber despite the packing of the same with a filler providing minutevoids, since air passages are provided which are substantiallycoextensive with the wall and are adapted to remove gas which mightotherwise tend to become trapped in local portions of the filler. Thebridges between the inner and outer metal wall portions are veryeffective in enhancing the insulating efliciency of the vacuum wall,since otherwise a comparatively large flow of heat would occur if themetal sheets of the inner and outer walls were joined to each other inthe conventional manner.

From the foregoing it will be evident that an important feature of theinvention consists in the unique construction of the bridges whichinterconnect the inner and outer walls around the boundary of the vacuumspaces, whereby heat conduction is minimized not only through theinsulation walls but also along the boundary bridges; that'low bridgeconduction may be attained by making the bridges of low conductivity,thin, or long, or with any two of these three characteristics, or withall three characteristics; and that a long bridge may be providedwithout increasing the spacing. between the walls by turning the bridgeback and forth in suitable contour as illustrated in Figs. 6 and 8.

While I have disclosed this invention particularly as applied to arefrigerating housing, it is evident that the principles thereof arewidely applicable to various installations where a heat insulating wallor jacket has proven or may prove desirable. Thus, for example, a vacuumchambered housing of this general type may be utilized in conjunctionwith heaters, ovens or boilers, while the walls of muses may similarlybe provided with hollow evacuated panels that are provided with pumpingmeans arranged as disclosed and described herein.

I claim:

1. In combination, a heat insulating housing, said housing having aswinging closure, the walls of the housing including the closure beinghollow and containing a gas pervious filler, a flexible gas ductconnecting the closure with one of the fixed walls of the housing, andair passageways extending along the filler and being substantiallycoextensive with the wall area of the housing, said passagewayscommunicating with the flexible gas duct and a second gas ductcommunicating with said passageways for connection to exteriorevacuating means.

2. A heat insulating housing having a hollow wall providing a vacuumchamber, a duct extending through the chamber, opposite face sheetshaving openings with their edges spaced from the duct,compression-receiving material of low heat conductivity surrounding theduct and extending between the face sheets, a thin metal sealing stripof low conductivity integrally connected to the face sheets to provide asubstantially air-tight seal, and a layer of non-conductive materialbetween said strip and the duct, whereby heat flow between the sheetsand the duct as well as between the sheets themselves is impeded.

3. An insulating wall providing a vacuum chamber and opposite metal facesheets, struts of material having low heat conductivity extendingbetween the sheets and bracing them against exterior pressure, metallicelements secured to the sheets and engaging end portions of the strutsto hold the latter in place, the intermediate part and one end of eachstrut being free from metal, whereby heat flow between the sheets isimpeded, and finely divided material packed between the sheets and aboutthe struts, said material aifording numerous small voids communicatingwith one another, the metallic elements being connected to one of saidsheets, a sheet of gas-pervious material adjoining the other sheet andcooperating therewith in defining gas passages, a duct communicatingwith said passages for connection to an evacuating pump.

4. A housing with an enclosure in the form of inner and outer shellshaving their margins connected to afford a hollow vacuum chamber, fillermeans comprising finely comminuted material between the shells opposingexterior pressure thereon, said material providing numerous minuteirregular, interconnecting voids, a duct connected to the interior ofthe chamber for connection to a vacuum pump, said filler meanscooperating with the-inner surface of one of said shells in definingregular, continuous air passages substantially coextensive with thatsurface of the shell, said passages being substantially larger than theinterconnected voids, the passages permitting the ready flow of gas tothe duct, whereby the resistance to gas flow from any part of thechamber to the duct is substantially determined by the resistanceafiorded by said voids to the flow of gas to the nearest of saidpassages.

DANIEL F. CQMSTOCK.

